after redirecting stdin still need to read data from keyboard

vrikers · 10-31-2004, 04:50 AM

hi, i'm a newbie !

please help me on doing the following :

a program (ipm) needs to receive data this way :
ps | ipm
(this command form is a MUST)

so the stdin in ipm will be ONLY what comes from "ps". how do i recreate(?) the stdin in order to read something from the keyboard ?

itsme86 · 10-31-2004, 04:54 AM

What will be reading from the keyboard? ps doesn't need keyboard input and you say that ipm will ONLY read ps's output....so where would the keyboard input be going?

vrikers · 10-31-2004, 05:00 AM

ipm needs to receive the process list.
after getting this list, the ipm program should wait for the user to specify a pid (by keyboard) and then kill it, or send some other signal to it.

and the only way that ipm can get the process list is by " ps | ipm " (it's a requirement).
how do i attach keyboard to stdin after this ?

itsme86 · 10-31-2004, 05:50 AM

I got this to work, but it will only work if you're logged in on pts/1

Code:

itsme@dreams:~/C$ cat inp.c
#include <stdio.h>
#include <string.h>
#include <errno.h>

int main(void)
{
  char buf[4096];

  while(fgets(buf, sizeof(buf), stdin))
    printf("Received: %s", buf);

  if(!freopen("/dev/pts/1", "r", stdin))
  {
    printf("Error reattaching stdin: %s\n", strerror(errno));
    return 1;
  }
  printf("Type something: ");
  fflush(stdout);
  fgets(buf, sizeof(buf), stdin);
  printf("You typed: %s", buf);

  return 0;
}

Code:

itsme@dreams:~/C$ ps | ./inp
Received:   PID TTY          TIME CMD
Received:  1591 pts/1    00:00:00 bash
Received:  2374 pts/1    00:00:00 ps
Received:  2375 pts/1    00:00:00 inp
Type something: it works
You typed: it works
itsme@dreams:~/C$

itsme86 · 10-31-2004, 06:11 AM

Here's a solution I found google'ing:
http:// http://www.lugod.org/...032.html 

Same concept, except they reattach to /dev/tty instead of /dev/pts/1. I'll leave the rest up to you

I'm interested in what you find out though, so if you could post your findings that would be great.